Honeybees in resting swarms respond to physical disturbances by changing the shape of the whole swarm, even if doing so comes at an individual cost, reports a paper published online this week in Nature Physics.
Bees are known to exhibit varied collective behaviours that prioritize the group over the individual. The so-called western honeybee (Apis mellifera Linnaeus) makes new colonies by swarming, in which a queen and some of her workers leave their hive to form a new one. While scout bees search for a suitable nesting site, the rest of the swarm cluster on a nearby tree, typically in the form of an inverted cone. The shape and density of this cone alters as the swarm responds to changes in the environment - withstanding high temperatures, rain, wind and predation to stay together as a cohesive superorganism.
To understand how swarms endure disturbances, Orit Peleg and colleagues attached conical clusters of honeybees to the underside of a board, which they shook with varying amplitudes, frequencies and durations. They found that horizontal shaking causes swarms to self-organize into flatter structures that are more mechanically stable than their initial conical shape.
Using particle-based simulations, the authors show that swarms can adapt by each bee individually responding to the strain it experiences by moving in the direction of increasing strain to maximize group stability. In this way, the bees’ physical interactions achieve the long-range signalling necessary for apparent collective intelligence. This result complements the traditional idea that collective behaviours arise from interactions through local chemical cues, which seldom confer long-range effects.